Re: Additional thunk for function

21 Sep 2007


      On 9/21/07, Victor Nazarov  wrote:
...
Here is some more details:
% ghc -c -ddump-stg T1.hs
==================== STG syntax: ====================
T1.map =
    \u []
        let {
          map1_sdR =
              \r [f_sdN ds_sdI]
                  case ds_sdI of wild_sdU {
                    [] -> [] [];
                    : x_sdM xs_sdQ ->
                        let { sat_sdT = \u [] map1_sdR f_sdN xs_sdQ; } in
                        let { sat_sdP = \u [] f_sdN x_sdM; } in  : [sat_sdP sat_sdT];
                  };
        } in  map1_sdR;
SRT(T1.map): []
% ghc -c -ddump-stg T1.hs -O
==================== STG syntax: ====================
T1.map =
    \r [f_sel ds_seg]
        case ds_seg of wild_ser {
          [] -> [] [];
          : x_sek xs_seo ->
              let { sat_seq = \u [] T1.map f_sel xs_seo; } in
              let { sat_sen = \u [] f_sel x_sek; } in  : [sat_sen sat_seq];
        };
SRT(T1.map): []
Sure, it makes sense that the extra thunk would be allocated when
optimization is disabled (if you don't pass in any optimization flags
like -O, it's like saying "don't do any optimization"). Don't expect
GHC to generate efficient code with optimization turned off :-)

Cheers,
Tim

-- 
Tim Chevalier * catamorphism.org * Often in error, never in doubt
"Other than to amuse himself, why should a man pretend to know where
he's going or to understand what he sees?" -- William Least Heat Moon